1. Field of the Invention
The present invention relates to electron beam lithography apparatuses and methods for compensating for electron beam misalignment, and more particularly to a technique for compensating for drawing position misalignment of an electron beam.
2. Description of the Related Art
An electron beam lithography apparatus has been proposed that uses an electron beam to draw elements constituting a pattern onto resist provided on a substrate in order to form a pattern of projections and depressions or the like when producing, e.g., a master carrier for magnetic transfer (Japanese Patent Application Laid-Open No. 2004-158287).
FIGS. 7A and 7B are a side view and a plan view of main parts of a conventional electron beam lithography apparatus respectively.
As shown, the electron beam lithography apparatus 1 includes: a rotating stage unit 20 including a rotating stage 14 supporting a substrate 12 with resist formed thereon and a spindle motor 18 having a motor shaft provided to align with the center axis 16 of the rotating stage 14; a shaft 22 penetrating part of the rotating stage unit 20 and extending in a certain radial direction R (Y) of the rotating stage 14; and a linear moving device 24 for moving the rotating stage unit 20 along the shaft 22. A precisely threaded rod 26 disposed in parallel with the shaft 22 is screwed in part of the rotating stage unit 20. The rod 26 is designed to be rotated in normal and reverse directions by a pulse motor 28. The rod 26 and the pulse motor 28 constitute the linear moving device 24 for the rotating stage unit 20.
The electron beam lithography apparatus 1 further includes an electron gun 30 emitting an electron beam EB, and a deflecting device having electrostatic deflecting plates 32 and 34 for deflecting the electron beam EB in a Y direction (the linear movement direction R of the rotating stage 14) and an X direction (the circumferential direction) orthogonal to the Y direction. The electron beam EB emitted from the electron gun 30 irradiates the resist on the substrate 12 via the electrostatic deflecting plates 32 and 34, a lens (not shown) condensing the electron beam, and so on.
A controller 36 controls driving of the spindle motor 18 (i.e., the rotation speed of the rotating stage 14), driving of the pulse motor 28 (i.e., linear movement by the linear moving device 24), ON/OFF of the electron beam EB from the electron gun 30, and deflection of the electron beam with the deflecting device having the electrostatic deflecting plates 32 and 34, thereby drawing desired patterns onto the resist on the substrate 12.
FIG. 8A is a plan view of the substrate 12 with desired patterns 38 (e.g., servo patterns for guiding a magnetic head onto a desired track) drawn thereon by the above-described electron beam lithography apparatus 1, and FIG. 8B is an enlarged view of a main part of FIG. 8A.
As shown in FIG. 8A, the patterns 38 including minute projections and depressions formed on a master carrier for magnetic transfer are arranged in a circular area excluding inner and outer peripheral portions of the substrate 12. These patterns 38 are formed in narrow-width regions extending in substantially radial directions from the center.
With part of a pattern 38 enlarged, as shown in FIG. 8B, an aggregation of minute elements 38a corresponding to information to be transferred constitutes concentric tracks T (T0, . . . , Ti, . . . ). When the recording method for the patterns 38 is of the type of a constant angular velocity of the rotating stage 14 (CAV), the circumferential length L of an element 38a is longer at the outer track T0 and shorter at the inner track Ti as shown in FIG. 8B as the sector length varies for the inner and outer peripheries. Inner elements 38a and outer elements 38a are arranged so that their start points align with a reference position of a rotation phase.
A basic aspect of a method for drawing an element 38a with the electron beam EB is as follows. As shown in FIG. 8B, while the substrate 12 is rotated in one direction A, the electron beam EB of a minute diameter scans in the circumferential direction X orthogonal to the radial direction (linear movement direction) R (Y) of the substrate 12 so that the shape of the element 38a is filled in, thereby drawing the rectangular element 38a at a predetermined phase position in a concentric track T (track width: W) extending microscopically linearly.
In this scanning, the electron beam EB is rapidly oscillated reciprocatively with a constant amplitude L in the circumferential direction X substantially orthogonal to the radial direction R (Y) while being deflected with a shift D in the radial direction R (Y). Thus, the electron beam EB sequentially draws the elements 38a by scanning them so that the shapes of the elements 38a are filled in with a triangular-wave trace. Once the electron beam EB finishes drawing for a lap of one track T, it moves to the next track T to draw in the same manner, thereby drawing the desired micropatterns 38 across the entire area of the substrate 12.
The track shift of the electron beam EB is performed by, for example, linearly moving the rotating stage 14 in the radial direction R (Y) for every n tracks (e.g., 16 tracks) corresponding to the maximum deflection range of the electron beam EB. The track-to-track shift within n tracks is performed by deflecting the electron beam EB.
When the electron gun 30 emitting the electron beam EB is of a fixed type, the rotating stage 14 is rotationally moved to shift the drawing trace during drawing of one rectangular element 38a. In this case, if the influence of the shifting is not negligible, it is necessary to deflect the electron beam EB with the shift D in the radial direction R (Y) while deflecting the oscillation center of reciprocative oscillation of the electron beam EB in the same direction as the rotation direction according to the rotation speed. Also, when the elements 38a of the patterns 38 are not rectangular but has a shape such as a parallelogram angled with respect to the track direction, it is necessary to deflect the electron beam EB with the shift D in the radial direction R (Y) while deflecting the oscillation center of reciprocative oscillation of the electron beam EB according to the angle.